In the ww1, why did Germany declare war on France and not some other country?
In WWI, Germany declared war on France so quickly into the war due to the belief that war between the two nations was inevitable and so they should declare war as quickly as possible to neutralize their enemy.
The theory and method of the invasion was largely centered around the Schlieffen Plan. This plan, devised in 1905 by Field Marshal Alfred von Schlieffen, relied on the fact that Russia would take at least three months to mobilize its forces whilst France would be able to mobilize immediately.
The plan centered around Germany attacking France immediately and sweeping through the country as quickly as possible in order to force a fast surrender before turning to face Russia. The plan failed largely due to the fact that it was heavily altered and modified which led to German troops not being able to defeat the French quickly and effectively. This led to a stalemate on the western front, which would take over four years to break.